Flexible duct with insulation holding means on coupling members

ABSTRACT

A flexible insulated duct comprising a wire helix wrapped with insulating material encased in a fluid-impermeable sleeve and terminated with connector members having impaling lugs that penetrate the insulating material and clinch the insulating material in place with respect to the connector members.

United States Patent Inventor Richard J. Bennett Pittsburgh, Pa.

App]. No. 784,455

Filed Dec. 17, 1968 Patented Feb. 23, 1971 Assignee P P G Industries,Inc.

Pittsburgh, Pa.

FLEXIBLE DUCT WITH INSULATION HOLDING MEANS 0N COUPLING MEMBERS 9Claims, 2 Drawing Figs.

US. Cl 138/147 Int. Cl F161 11/02 Field of Search 138/147,

[56] References Cited UNITED STATES PATENTS 1,223,835 4/1917 Schmus138/147 3,216,459 11/1965 Schroeder et a1..... 138/139 3,394,737 7/1968Hoffmann et a1. 138/109 Primary Examiner-Louis D. RimrodtAttorney-Chisholm & Spencer ABSTRACT: A flexible insulated ductcomprising a wire helix wrapped with insulating material encased in afluid-impermeable sleeve and terminated with connector members havingimpaling lugs that penetrate the insulating material and clinch theinsulating material in place with respect to the connector members.

" PAT-ENIED FEBN |97| 5 2 INVENTOR RICH/9RD J. J'ENNETT FLEXIBLE DUCTWITH INSULATION HOLDING MEANS ON COUPLING MEMBERS BACKGROUND OF THEINVENTION This invention relates to flexible insulated duct for theconduction of gaseous fluids in commercial or residential heating and/orair conditioning systems. More specifically, the present inventionrelates to flexible insulated duct comprised of a helically wound wirewrapped with porous insulating material encased in a flexible,fluid-impermeable sleeve and terminated with sheet metal connectormembers having means to clinch the insulating material in place.

The present invention is an improvement over flexible duct constructionssuch as those disclosed in copending application Ser. No. 701,301,entitled Flexible Duct," filed Jan. 29,1968 by Malcolm Hay, Jr., nowU.S. Pat. No. 3,502,114 copending application Ser. No. 760,171, entitledLongitudinally Reinforced Flexible Duct," filed Sept. 17, 1968 byWilliam .L. Runshe and Clarence H. Helbing, and copendingapplicationSer. No. 784,456, entitled Flexible Duct With Interlocking- TypeCoupling," filed Dec. 17, 1968 by Clarence H. Helbing, Richard J.Bennett, Frank E. Wilson, Alphonso C. Pecora, Malcolm Hay, Jr. andWinfield T. Irwin all assigned to the assignee of the present invention.

As disclosed in the aforesaid copending applications, flexible ductconstructions have previously been proposed which are comprised of adimensionally unstable wire helix terminated with connector members andhaving a circumferential blanket of insulating material'adhesivelybonded to the helixand the connector members. Flexible ducts of theabove type of construction have a number of distinct advantages overother types of flexible duct construction. However, it has now' beenfound that flexible ducts of the above type of construction may besusceptible to serirYus damage by reason of high axial and/or torsionalforces being imparted to one or both of the connector members duringnormal handling or use.

Flexible ducts constructed in the above manner rely principally upon theshear strength of the blanket of insulating material at the surface ofthe blanket which is adhesively bonded to the connector members toresist separation of the connector members from the insulating material.Under certain conditions, and in particular under high axial and/ortorsional loads, this shear strength has not always been found to beadequate. Accordingly, separation may occur, and this separation mayeither be partial or complete. Obviously, the extent of the separationdetermines the extent to which the duct section will be weakenedthereby. If complete separation occurs, the duct section is generallyconsidered to be unfit for use. However, if less than completeseparation occurs, it is uncertain as to whether it will be note noticedor not, and too frequently such separation goes completely unnoticeduntil a subsequent failure of the duct section occurs. The presentinvention proposes to overcome the aforementioned deficiencies of priorart flexible duct construction by providing flexible insulated duct withconnector members.

having impaling lugs projecting outwardly from the outer surface thereofto penetrate the insulating material and clinch the insulating material'in place with respect to the connector members. In accordance with thepresent invention, the coupling members become so integrated with theadjacent-insulating material that they essentially function as a unittherewith. Thus, in thepractice of this invention, it is possible totake greater advantage of the physical strength characteristics of theinsulating material, including the aforementioned surface shear strengththereof,-before complete separation of the connector members from theinsulating material can occur.

The foregoing and other objects, features and advantages of thisinvention will become more apparent when considered in connection withthe accompanying drawing, in which:

FIG. 1 is a perspective view, broken away, of a short section offlexible insulated duct provided with connector members embodying theprinciplesof this invention; and

FIG. 2 is a perspective view of the duct of FIG. 1 prior to beingwrapped with insulating material and encased in a flexible outer sleeve.

Depicted in the drawing is a flexible duct construction embodying theprinciples of the present invention. Broadly, the flexible ductconstruction shown is composed of a wire helix 14 wrapped withinsulating material 18, encased in a flexible, fluid-impermeable sleeve20 and terminated with male and female connector members 10 and 12having impaling lugs or projections 13 that penetrate the insulatingmaterial and clinch the insulating material in place. As shown in FIGS.I and 2, connector members 10 and 12 may be interlockingtype connectors.Also as shown in FIGS. 1 and 2, longitudinal reinforcement 16 may beemployed in the construction of the flexible duct of this invention toenhance the axial tensile strength strength of the duct.

With particular reference to FIGS. 1 and 2, the manufacture of the ducttherein shown proceeds'by mounting the pair of interlocking-typeconnector members 10 and 12 at spaced locations on a collapsible mandrel(not shown). An end of the wire forming the wire helix is then affixedto one of the connectors, e.g., the female connector member 12, and ishelically wound around a length of the connector, along the length ofthe mandrel,(not shown) and around a length of the other connectormember, e.g., the male connector member 10. During winding, an adhesivecoating is continuously applied all along the length of the wire formingthe helix 14. Upon reaching the desired length, the wire is terminatedand the free end is af fixed to the other connector member, e.g., themale connector member 10.

One or more flexible cordlike tensionmembers 16 are then placed over thewire helix and affixed at their .ends to connector members 10 .and 12.Preferably, at least a pair of tension members 16 are used and areaffixed to the connector members apart so that thereinforcement.is-parallel to the axis of the helix. A blanket ofinsulating material 18 is next sprayed with an adhesive that covers asufficient portion of one surface thereof to provide at least onecircumferential wrap around the wire helix. The insulating blanket I8 isthen wrapped con volutely or circumferentially around the connectors 10and 12, the wire helix 14 and the longitudinal reinforcement 16 so thatthe adhesive coated surface faces the interior of the duct.

. As the insulating blanket I8 is wrapped around the connector members10 and 12, one or more circumferential wraps of the blanket are impaledon upstanding lugs 13 provided on each of the connector members. Thefree ends of lugs I3 are then preferably bent towards the nearestadjacent end of the duct, i.e., away from the center of the duct, untilthey lie essentially parallel to the axis of the duct. This clinches theinsulating blanket in place with respect to each of the connectormembers. Subsequent wraps of the'insulating blanket may then be wrappedover the bent lugs.

Preferably, the insulating blanket covers substantially all of thefemale connector 12 and only a portion of the male connector 10. Afterwrapping, the trailing end of the insulating blanket is preferablysecured in place by means of staples (not shown). An outer sleeve offlexible fluid-impermeable material 20 is then pulled over theinsulating blanket and the mandrel is collapsed to release the finishedsection of duct.

In the practice of the present invention, many different materials canbe used to produce the helix element of the duct. As disclosed in theaforementioned copending applications, the helix material should beresistant to atmospheric corrosion, should possess sufficient strengthand rigidity to prevent collapse of the duct in a radial direction uponapplication of moderate pressures, but should not be so strong as toadversely affect the flexibility of the duct. The helix material shouldalso be sufficiently elastic to cause spring-back of the duct to itsoriginal shape as soon as external deforming prcssures on the duct arerelaxed. The desired helix material should exhibit, then, a balance ofgood flexibility, elasticity and strength. Any material roughlyconforming to the form of a slender rod or wire composed of metal,plastic or a combination thereof, having a. circular or noncircularcross section and exhibiting a suitable balance of these characteristicscan be used.

Galvanized hard-drawn steel spring wire has been found to be anexcellent helix material. For ducts 9 inches or less in inside diameter,a galvanized wire of 0.041 inch in diameter is preferred. For ducts from10 to 18 inches in inside diameter, a wire 0.051 inch in diameter shouldbe used. In all duct sizes, the preferred spacing of the convolutions ofthe wire helix is three-fourth of an inch from center to center,although the spacing may range from one-fourth to 1% inches and stillproduce a suitable duct.

FIGS. 1 and 2 show the wire helix fastened to connectors or couplings land 12. In accordance with the aforesaid copending applications,connectors or couplings and 12 are provided with tab means, hereinafterdescribed, for fixing and stabilizing the ends of the wire helix 14 andthe longitudinal reinforcement 16. In each of the embodiments shown inthe drawing, the male connector 10 and the female connector 12 bothcomprise a galvanized sheet metal sheet sleeve or coupling ofcylindrical cross section. For suitable resistance to atmosphericcorrosion, the zinc-coated (galvanized) sheet steel and steel wire usedin the construction of the duct of this invention preferably has aunifonn zinc coating of about 0.3 ounce per square foot of surface areacoated (0.6 ounce per square foot of sheet), as determined by theStandard Method of Test for Weight of Coating on Zinc-Coated(Galvanized) lron or Steel Articles, ASTM Designation A90-53.

Projecting from the outer surface of each connector, there is shown anopen tab or loop 22 that forms an integral part of the connector and ispreferably produced by a simple stamp ing operation, such as bypunch-pressing a small portion of the connector material outwardly fromthe remainder of the connector material. As shown, the ends of the wirehelix are inserted through the loops 22 and the 'wire is then twisted onitself to firmly secure the ends of the wire to the connectors andthereby stabilize the ends of the wire helix.

Also projecting from the outer surface of the connectors are open tabsor loops 24 that provide means for attaching longitudinal reinforcement16 to the connectors. During manufacture of the duct, these tabs orloops 24 are longitudinally aligned on the mandrel so that thereinforcement 16 is subsequently attached to the connectors parallel tothe axis of the duct. Shown in F168. 1 and 2 are two longitudinalreinforcement members 16. For this purpose, as best shown in FIG. 2, apair of tabs or loops 24 spaced 180 apart are provided on each of theconnectors.

One preferred longitudinal reinforcement 16 that is usable with all ductsizes is galvanized steel wire of 0.04 inch diameter. As shown in thedrawing, the ends of the wire reinforcement 16 are inserted through theloops 24 and the wire is then twisted on itself to firmly secure theends of the wire to the connectors, thereby longitudinally reinforcingthe wire helixconnector complex against tensile forces tending toseparate the connectors and straighten the wire forming the helix 14.

Another longitudinal reinforcement (not shown) that may be used in lieuof steel wire is a nominal one-eighth inch fiber glass cord terminatedwith aluminum tubing or sleeves. The sleeves are preferably about 2inches in length and are compressed or flattened to firmly secure thesleeves around the ends of the cord. The sleeves are then insertedthrough loops 24 on connector members 10 and 12 and bent into a hookshape to clinch the sleeves around loops 24, thereby securing the cordreinforcement to the connector members.

With respect to each of the flexible cordlike tension members, theparticular wire and wire size, as well as the particular cord material,cord size and cord attachment means selected, should each be chosen witha view towards maintaining the flexibility of the duct, i.e., itsbendability and twistability, while providing the duct with sufficientlongitudinal strength to withstand at least a 50-pound axial tensileload for 24 hours. Moreover, the materials used in the tension membersshould each be chosen so that they are resistant to atmosphericcorrosion. Also, these materials should be used only in combinationsthat would not cause any detrimental galvanic action which wouldadversely affect any part of the system formed from such materials.

The connector members 10 and 12, shown in FIGS. 1 and 2. areinterlocking-type members that are provided with coupling means whichpermit rapid and positive interlocking of adjacent duct sections, yetmeans capable of being manually manipulated to permit ready uncouplingof adjacent duct sections, if desired.

More particularly, the embodiment of interlocking-type connector membersshown contemplates providing the male connector member 10 with couplingmeans comprising a plurality of slots or apertures 28, and the femaleconnector member 12 with coupling means comprising an equivalent numberof cars or dimples 30 that are struck up from the sheet metal so thatthey project inwardly toward the interior of the connector member 12. Inthe embodiment illustrated. three generally rectangular slots 28 areprovided on male connector 10. Each slot 28 is lineally spaced an equaldistance from the free end of connector 10 and angularly spaced an equaldistance from each other, i.e., apart. Similarly, female connector 12 isprovided with three essentially semihemispheroidal shaped ears 30, eachof which is lineally spaced an equal distance from the free end ofconnector 12 and angularly spaced an equal distance from each other. Asshown, slots 28 are preferably disposed closer to the free end of connector 10 than ears 30 are disposed relative to the free end ofconnector 12.

As will be apparent, male connector member 10 is slightly smaller inexterior circumference than the interior circumference of femaleconnector member 12. Accordingly, when a male connector 10 on one ductsection is inserted into a female connector 12 on another duct section,the free end of connector 10 cams overt over the inclined surfaces ofears 30 until the leading edges of slots 28 drop behind the verticaltrailing edges of cars 30. in this position, slots 28 are disposed incircumscribing relation about ears 30 and male connector 10 ispositively interlocked with female connector 12. The interaction betweenthe leading edges of slots 28 and the vertical trailing edges of ears 30prevents direct axial disengage ment of the connector members. However,should it thereafter be desired to remove male connector 10 from femaleconnector 12, this can be readily accomplished by simply rotating oneconnector member with respect to the other so that side edges of 28 camover the inclined surfaces of cars 30 to a position where slots 28 areclear of ears 30 and the connector members can then be longitudinallydisengaged.

in accordance with the present invention, connector members 10 and 12are provided with one or more upstanding lugs 13. In the embodimentshown, connector members 10 and 12 are each provided with a pair ofupstanding lugs 13, spaced apart. Lugs 13 provide means for clinchingthe insulating blanket in place with respect to each of the connectormembers l0 and 12. As shown, lugs 13 are trapezoidal in shape and arestruck up from the sheet metal connectors so that they are disposedgenerally perpendicular to the longitudinal axis of the final duct.Since the fibers forming the insulatinblanket 18 tend to be orientedpredominately perpendicular to the longitudinal axis of the final duct,i.e., circumferentially of the duct, lugs 13 can penetrate insulatingblanket 18 with minimum resistance. In all duct sizes, trapezoidal lugs13 are preferably about 1 inch X five-eighths inch X l inch high.

As the insulating blanket I8 is wrapped around the connector members 10and 12, one or more circumferential wraps of the blanket are impaled onupstanding lugs 13. The free ends of lugs 13 are then preferably benttowards the nearest adjacent end of the duct, i.e., away from the centerof the duct, until lugs 13 lie essentially parallel to the axis of theduct. Alternatively, the free ends of lugs 13 could be bent towards thecenter of the duct. In either case, lugs 13 penetrate and clinch theinsulating blanket in place with respect to each of the connectormembers. Lugs 13 preferably extend completely through the thickness ofinsulating blanket 18, although they fabrication to bond the helix andconnector members to the insulating blanket may be any conventionallyused adhesive, although a nonflammable type is preferred for safetyconsiderations. Nonflammable adhesives are preferred also because theyare frequently required by local building codes and ordinances. Theadhesive used should remain flexible, even after setting, so that theduct may be flexed without permanently damam'ng the bond, as may occurduring installation of the duct. The adhesive used should also have acomposition which does not attack or corrode the material of theinsulating blanket.

The preferred adhesive is a neoprene elastomer and resin adhesive. Othersuitable adhesives that may be used are disclosed in the aforementionedapplication, Ser. No. 701,301 Also, as disclosed in said application,the same adhesive may be used on the blanket material as that applied tothe wire helix. The only modification made is that the adhesive isthinned somewhat so that it may be easily sprayed on the blanketcomposite.

The insulating material preferably employed in the improved duct of thepresent invention should have a density of not less than aboutthree-fourths of a pound per cubic foot and a tensile strength of notless than about 6 pounds per square inch in the longitudinal directionof its formation and not less than about 2 pounds per square inch in thetransverse direction of its formation. One particularinsulating materialthat fully meets the foregoing characteristics is a coherent, strandindividual fiber composite insulating material in which individual glassfibers and glass fiber strands are randomly oriented and uniformlydistributed throughout the other and bonded together by a thermosettingresinous binder. This insulating material and its method of manufactureare fully disclosed in the aforesaid copending application, Ser. No.701,301, the disclosure of which is incorporated herein by reference.

The wire helix, since it is dimensionally unstable in the iongitudinaldirection, must be firmly bonded to the insulating blanket to maintainthe spacing between convolutions. Furthermore, the bond between the wirehelix and the insulating blanket must be sufficiently strong to permitflexing and unflexing of the duct without collapse or without decreasingthe internal cross-sectional areaof the duct, to avoid restricting fluidflow. The strand-fiber composite blanket material mentioned abovedevelops the required strength in the duct because ofits superiorability to adhere its mass to the helical wire element of the duct whileat the same time maintaining a strong internal bond between the variouscomponents of the blanket material.

r The flexible sleeve material employed with this invention can compriseany flexible substantially nonexpandable material such as polyvinylchloride. The preferred sleeve material is a 3.0--3.35 mil thickextruded polyvinyl chloride tubing.

Other materials, such as a polyvinylene chloride film, a

laminatmi polyvinyl chloride film and fiber glass scrim fabric materialand various neoprene impregnated glass cloths may also be used. a

As will be apparent from FIG. 1, it is desirable that the finished ductsection have the insulating material and flexible sleeve essentiallycompletely covering the female connector 12 and only partly covering themale connector 10, so that when joined with other duct sections or thelike, there is pro vided a continuous cylindrical covering of insulatingmaterial and sleeve material about the duct. Preferably, in the ductconstruction heremabove described, coupling means 28 and 30 are locatedsuch that, when a connector member 10 on one duct section is interlockedwith a connector member 12 on another duct section, the abutting edgesof insulating material covering the respective connector members areslightly compressed to assure a continuous covering about the duct.

Additionally, the flexible sleeve material 20 may be somewhat longerthan the insulating material 18, and the extra length of material (notshown) may be folded back on itself at one end of the duct section, sothat by unfolding this extra length there is provided an overlap ofsleeve material 20 at each joint between adjacent duct sections. Thislap joint of sleeve material is preferably taped to enhance the desiredfluid and vapor impermeability of flexible duct construction.

It will be apparent from the foregoing that the present inventionprovides an improved flexible duct construction having connector membersthat are provided with peripherally disposed lugs to clinch theinsulating material of the duct to the connector members. Accordingly,in the final duct of this invention, the insulating material acts as asignificant loadbearing member to resist damage to the duct as a resultof axial forces and/or torsional forces being imparted to one or' bothof the connector members during normal handling and use. In accordancewith the practice of this invention, any uncertainty that mightotherwise have existed as to whether the connector members are securelyafiixed to the insulating material is completely avoided. The practiceof this invention positively assures providing a strong bond between theinsulating material and the connector members, and thereby greatlyenhances the reliability-and structural integrity of the duct section.Also, the duct of the present invention retains the desired flexibility,good air flow characteristics, competitive price and desirableacoustical characteristics of earlier flexible duct designs.

While a preferred embodiment of this invention has been illustrated anddescribed, it will be understood that various changes and modificationsmay be made within the scope of theappended claims without departingfrom the spirit of the invention.

1 claim:

1. A flexible insulated duct comprising a wire helix wrapped with ablanket of fibrous insulating material, encased in a flexible,fluid-impermeable sleeve and terminated with connector members havingimpaling lugs that penetrate at least one wrap of the insulatingmaterial and clinch the insulating material in place with respect to theconnector members.

2. The flexible insulated duct of claim 1 wherein the impaling lugs arebent towards the ends of the duct.

3. The flexible insulated duct of claim 1 wherein the impaling lugs arebent towards the center of the duct.

d. The flexible insulated duct of claim 1 wherein at least onesubsequent wrap of said insulating material is wrapped over saidimpaling lugs.

5. The flexible insulated duct of claim 1 wherein the insulatingmaterial is bonded together by a thennosetting resinous binder.

6. The flexible insulated duct of claim 5 wherein the insulatingmaterial has a density not less than about three-fourths of a pound percubic foot.

7. The flexible insulated duct of claim 6 wherein the insulatingmaterial has a tensile strength of not less than about 6 pounds persquare inch in the longitudinal direction of its for mation.

8. The flexible insulated duct of claim 6 wherein the insulatingmaterial has a tensile strength of not less than about 2 pounds persquare inch in the transverse direction of its formation.

9., The flexible insulated duct of claim 6 wherein the insulatingmaterial is a coherent, strand individual fiber composite insulatingmaterial.

1. A flexible insulated duct comprising a wire helix wrapped with ablanket of fibrous insulating material, encased in a flexible,fluid-impermeable sleeve and terminated with connector members havingimpaling lugs that penetrate at least one wrap of the insulatingmaterial and clinch the insulating material in place with respect to theconnector members.
 2. The flexible insulated duct of claim 1 wherein theimpaling lugs are bent towards the ends of the duct.
 3. The flexibleinsulated duct of claim 1 wherein the impaling lugs are bent towards thecenter of the duct.
 4. The flexible insulated duct of claim 1 wherein atleast one subsequent wrap of said insulating material is wrapped oversaid impaling lugs.
 5. The flexible insulated duct of claim 1 whereinthe insulating material is bonded together by a thermosetting resinousbinder.
 6. The flexible insulated duct of claim 5 wherein the insulatingmaterial has a density not less than about three-fourths of a pound percubic foot.
 7. The flexible insulated duct of claim 6 wherein theinsulating material has a tensile strength of not less than about 6pounds per square inch in the longitudinal direction of its formation.8. The flexible insulated duct of claim 6 wherein the insulatingmaterial has a tensile strength of not less than about 2 pounds persquare inch in the transverse direction of its formation.
 9. Theflexible insulated duct of claim 6 wherein the insulating material is acoherent, strand individual fiber composite insulating material.